David Cameron has sought to wrest back the political initiative ahead of the general election by launching a plan to allow workers to run their public services and unveiling posters targeted exclusively at those who have never voted Conservative.

On the first Monday of the parliamentary recess, the Tory leader and his shadow Chancellor took to the dystopian setting of Battersea Power Station where they unveiled three new-look posters. With the line, "I've never voted Tory before, but …" three voters give their reasons for being attracted to David Cameron's party. One reads: "I've never voted Tory before, but we've got to mend our broken society".

Speaking at the launch today, Cameron said: "We are not the same old Conservative party. We are the party of the mainstream majority in our country."

The party insists that this week was always marked in the grid as the time to target swing voters, and indeed Labour or Liberal Democrat voters, but the new pictures are markedly different from the party's earlier emphasis solely on David Cameron. That poster campaign backfired within hours when it emerged the Tory leader's picture had been airbrushed and, running with the strapline "I'll cut the deficit, not the NHS" was assessed to have been both too presidential and too austere, but the new tack comes after a run of stories suggesting the Tory high command may be seen as too aloof by both its backbenches and grassroots.

In terms of policy, the party announced a Conservative government would give more power to public sector workers enabling state employees in primary schools, social work, call centres, Jobcentre Plus offices and nursing teams to run their own co-operatives with public money.

Cameron said the plans would unleash "a new culture of public sector enterprise and innovation"; able to "share" any financial surplus among the staff and which would amount to "the biggest shift of power from government to people since the right to buy your council house in the 1980s".

He said: "I know that there are millions of public sector workers that work in our public services and who frankly today feel demoralised, feel disrespected, feel a lack of recognition.

"We will not only get rid of those targets and that bureaucracy that drives you so mad, we will give you the power in a way that is as radical as the right to buy your council home … We would say: 'Here is your budget, deliver this service, and if you do it more efficiently and more effectively, you can keep some of the savings that you make.'"

"All the evidence shows that this kind of co-operative, bottom-up partnership leads to high productivity, low staff absenteeism, and much higher staff morale."

At his news conference today, Cameron also pledged to iron out a wrinkle currently hampering the government's own attempts at mutualising the public sector. Any workers joining a co-operative, he said, would be protected by TUPE, the Transfer of Undertakings (Protection of Employment) regulations that protect employment rights when a new employer takes over a business.

It has been known for some time Labour would pledge similar ideas in its manifesto. The government has already set up foundation trusts which operate on a mutual principle, and allowed nurses the right to request mutual status. By the end of the year, the schools secretary, Ed Balls, has said he will have seen 200 co-operative schools set up.

Last week, Tessa Jowell, the Cabinet Office minister, held a large mutuals meeting in Downing Street.

Today a government aide said: "They're saying 'we like the government's policy'. Well, thank you very much but we're already doing much of this except we want the mutuals to be genuinely mutual composed of both staff and users whereas the Tory plans appear to be staff."

Michael Stephenson, the general secretary of the Co-operative party – which is affiliated to Labour – said the Tory model gave scant consideration of the community in which the employee-owned service would operate.